|Class D Switching Power Amplifiers and Power D/A conversion|
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|3rd February 2005, 07:50 PM||#1|
Join Date: Apr 2003
Sonic Impact 5066 Parts List & Modifications
Here's some data on what I've managed to pull from one of my Sonic Impact 5066 boards. This information should not be taken as gospel -- it's my best attempt to decipher the workings of the board.
Sonic Impact 5066 Parts Description, correlating to tripath datasheet
This information is based on a Sonic Impact 5066 board with the date code of 2003.07.03
Parts with a (?) next to them indicate my best guess of this part's value and/or purpose. Many of the capacitors on the bottom side of the board, toward the speaker outputs, are most likely part of the output correction stuff on the datasheet. I was also unable to locate any schottky diodes on the output, as listed in the datasheet, but this may be my inability to decipher some of the surface mount parts.
(from Left to Right):
V + Ro Lo G Li Ri
V = switch 12volt out
+ = switch 12volt in
Ro = to volume from right channel
Lo = to volume from left channel
G = ground
Li = from volume control to amp left channel
Ri = from volume control to amp right channel
The LED is mounted to bottom. Looking down from the top, the cathode (notched side) is on the left.
Connector #2 (12V)
Looking at the board from the top, with the wide side closest to you, the pins are as follows (front top to bottom):
Pin 1 (Top, Center): 12V in
Pin 2 (Middle, to the right): Ground disconnect for battery source. This pin opens the grounding between the battery and the rest of the board when a plug is inserted
Pin 3 (Bottom, Center): Ground
If you decide to remove the 12V jack, and don't care about destroying it, the easiest way I've found is to do as follows:
1) Using desoldering braid or a desoldering iron, remove as much solder from each of the pins as possible.
2) Using snips, cut the tabs off the bottom of the jack
3) Reheat the solder pad on pin3 and pull the connector from the back of the board towards the front. Then proceed in order through Pin2 and Pin 1.
Connector #3 (Audio in)
Looking at the board from the top, with the wide side closest to you, the pins are as follows (left to right):
Pin 1: Right channel in
Pin 2: Ground
Pin 3: Ground
Pin 4: Left channel in
Pin 5: Ground (located in the center of the connecter, below the other 4 pins)
t = top
b = bottom
VR1 = 50k (volume control, measured 45k5)
R01t = 10k (103), Right channel in, connected to ground
R1t = 1k5 (152), Current limiting resistor for LED
R2t = 20k (203), Ri - Inverting Input Resistor, Left Channel
R4t = 36k (363), Rf - Feedback Resistor, Right channel
R02b = 10k (103), Left channel in, connected to ground
R1b = 20k (203), Ri - Inverting Input Resistor, Right Channel
R3b = 8k2 (822), Rref - Reference Resistor to pin 6
R5b = 36k (363), Rf - Feedback Resistor, Left Channel
R8b = 10 (100), Output Zobel, Right Channel
R9b = 10 (100), Output Zobel, Left Channel
C5t = 0.1uF?, Cs - Low Voltage Bypass, connects to pin 1, 4 and 9
C7t = 0.1uF?, Cd - Charge Pump input cap, pin 2-3
C10t = 330uF/16v, Csw - Supply Decoulping for H-bridge Supply Pins
(This cap supplies Vdd1 and Vdd2, as they are connected under the chip.)
C9b = 1uF, Cpump - Charge Pump Capacitor
C11b = 0.1uF?, Csw - Local supply decoulping for H-bridge
C12b = 0.1uF?, Csw - Local Supply decoupling for H-bridge
C17b = 0.22uF?, CDo - output zobel, right channel
C18b = 0.22uF?, CDo - Output zobel, left channel
C21-24 = 0.47uF?, Co - Output Capacitors
The large solder blobs on the board are connected to the ground plane as far as I can tell. The grounding is connected to the bottom of the chip by a large number of vias underneath. This is similar to the Powerpad(?)-style mounting of a headphone amp chip from Texas Instruments.
|3rd February 2005, 08:09 PM||#2|
Join Date: Apr 2003
Here's my list of suggested modifications based on the datasheet and what I've seen other modders do:
1) Remove volume control and either wire it directly to your input jacks (dedicated amp) or wire it to a better one (integrated amp). Basically, get rid of the volume board.
2) Remove the power and audio input jacks. Wire your inputs directly to the pads described above. I wired the +12V in on mine directly to the switched 12v in, and the ground to pin 3 on the power jack.
3) Replace R4/R5 to 20k resistors. This sets it to the "ideal" 12V/V listed in the datasheet (Vinnie R states that he does this mod on his Clari-T mod of the Sonic Impact). Currently, the gain is set to 21, this mod would reduce it to 12 (I think.. I'm not an EE, so if this is incorrect, someone please let me know).
4) Replace C10. I replaced this with a Panasonic FC 16v cap that I had laying around. Vinnie R implies that he desolders C10, C11 and C12, and then solders "two" C10's of either 1500uF or 1800uF, one each directly to VDD1 and VDD2. These are then bypassed with 0.1uF surface mount caps on the caps.
I think this is unnecessary. C11 and C12 are already extremely close to the input pins. VDD1 and VDD2 are already interconnected underneath the chip (I dissected one SI board to confirm this!). Therefore, I think connecting a 1500uF or 1800uF cap directly to one of the pin sets would be sufficient. I can't see any harm in adding it to both pins, but I think you definitely run into the law of diminishing returns. For the ground path on this cap, just hook it into one of the giant solder blobs near the chip.
5) Replace R01t, R2t, R4t, R02b, R1b and R5b with better quality resistors. I don't think the ones on the board are of particularly high tolerences. 0.1% surface mount chips are extremely inexpensive, so this could be a good replacement.
6) Replace the input and output connectors. I think this one is pretty much a given. The spring clips for the speaker-outputs are pure ****. The input via 1/8" jack is fine for portable applications, but useless for home apps. I'm presently using jrsun's WBT-like RCA's and Binding posts.
7) New Case. I think this one is also a given. I'm presently using a Context Engineering case for mine (I'll try to post pictures later).
If anyone else has suggestions, please contribute! Hopefully with the parts list above it will help other folks come up with ideas for mods!
|3rd February 2005, 08:19 PM||#3|
Join Date: Apr 2003
AC power supply possibilities
My current thought on an external, AC power supply on the cheap consists of the following:
2.4A, 15VAC wall transformer:
Digi01's Positive Regulator Board
my regulator pcb
I'm outfitting the regulator board with a LM1085 voltage regulator set to 13V, along with a 12,000 uF 35v cap and MUR860 diodes.
I haven't completed mine yet, but I think that this is a pretty good set of suggestions. The total cost is probably $30, and I think it will beat the pants off any readily available regulated power supply near that price.
I'll let folks know how mine sounds once it's completed.
|6th February 2005, 06:22 AM||#4|
Join Date: Feb 2007
Well done - this is exactly the type of information that aids all DIY . Hope to hear how your mods sound.
You are one mother
|6th February 2005, 05:25 PM||#5|
Join Date: Oct 2003
Great post. Your research is very, very helpful!
I was also thinking of using digi1's regualtor board for the PS, but most likely for ones I'll be making for friends and family who don't want to deal with a battery.
Are you going to try CarlosFM's snubberized PS on the Sonic Impact? This was originally intoduced by Carlos for use with the gainclone amps. According to a members who's tried it, it works well for these digital amps, as well.
Apparently the snubberized design sounds just as good as a regulated supply (and even better according to Peter Daniel).
I like the snubberized supply because it alleviates the heat issues that sometimes regulated supplies have. I like this idea because the less heat, the better the longevity and reliability of the amp. And if it sound just as good or even better, well, hey!
Of course, the regulated supply will be somewhat smaller because it doesn't require as many large caps. With the results said to be equal or better, I like the passive solution better, myself.
Please let us know how your tests go.
|6th February 2005, 07:00 PM||#6|
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
|6th February 2005, 08:06 PM||#7|
I use the SA to run my mids and Aurum Cantus 2si ribbon tweeter.
The sound is incredible, BUT I recently noticed that the highest highs such as cymbols lose their distinctive sounds and are more like a sizzle sound rather than brass being hit. Same for cowbells, the sound is a bit like a CD mistracking (exagerating a bit here...)
Now that I've note this it bugs me. I use a stock SA with a wall wart supply. Will any of these mods help this?
For bass I use my gainclone, so the weak bass doesn't affect me.
Next S.F. Burning Amp Festival To Be Announced
Burning Amp thread here on diyAudio
|6th February 2005, 11:37 PM||#8|
Join Date: Apr 2003
Thank you. I was trying to find this information myself, but have yet to see anyone post anything like this. I think Vinne R might have this info, but since he's trying to create a commercial endeavor off of mods to the SI, it's probably not in his best interest to post this =)
I'm definitely going to use a regulated PSU. The Gainclone has a pretty wide tolerence on what voltages it will handle, the Tripath chip doesn't. I'm setting my regulated PSUs to 13v dead even. Batteries usually sit at ~13.2v when fully charged.
Also, you only need 1 regulator for this chip. I'm using a 12,000 uF 35v Nichicon LS(M) before the regulator, and a 16v 470uF Nichicon HE(M) after the regulator. I may need to add a snubber/zobel(?) post-regulator to keep it stable -- I'm not sure if using the HE(M) will destabilize the regulator. The 35v 12,000uF caps are available from Apex Jr. (2 for $1!). Even if you just went with a snubberized version, you'd only be adding an additional cap and resistor to this.
Finally, as for the heat issues, if you go with one of the nice cases provided by AMT, you could probably just bolt the regulator to the case with a mica insulator and some heatsink goop with no problems. For $50 or so, I think his case is a fantastic bargain (I have to remember to e-mail him to buy a few!).
My lightly modded (new case, 10k noble volume pot and 680uF Panasonic FC in place of the original 330uF no-name cap) sounds absolutely fantastic. I'm still only powering it off the AA batteries. I'm using some Acoustic Research AR-17 speakers. These speakers have a Aluminum midbass coated with magnesium, and a titanium dome tweeter coated with diamond dust. Basically, it's unforgiving on badly recorded material and will show a spitty sound with bad electronics. I haven't noticed this at all with the SI, though.
My hunch is that your ribbons might be picking up some of the remnants of the high-frequency hash from the switching frequencies on the chip.
I'm in the process of picking up new parts from Digikey to finish up a newly modded one to compare against my lightly modded "benchmark". This list right here is only a list of the mods done to the board itself, not to the chassis/etc:
1) 4x 20k and 2x 10k 0603 surface mount resistors (0.1%):
The 20k resistors will replace R2t, R4t, R1b and R5b, while the 10k will replace R01t and R02b.
2) Removal of C4 on top and C3 on the bottom from the board. I'll bridge these traces and then mount the input caps offboard. I'll be using 5.1uF Solens for this.
3) Mount 1x 2200uF Panasonic FM cap as close as possible to the chip (probably to one of the pins), and removal of the 330uF cap in position C10t. The Panasonic FM cap is available here:
If you want to use something that fits in the original spot, the largest cap that will fit there is 8mm in diameter, so you're limited to a 680uF cap from panasonic. Nichicon's HE series might have something that fits there, though. Digikey's has the 680uF panasonic FM here:
4) Replace the 0.01uF output caps across the speaker terminals with 1% tolerance Polypropylene caps:
I think these mods will get the board a lot closer to it's full potential. After that, short of a redesign of the board itself, I don't think we'll be able to improve on it much more.
If anyone else has any suggestions, let me know -- I'll be placing my order with Digikey tomorrow. Good luck with your mods everyone!
|7th February 2005, 11:59 PM||#9|
Join Date: Dec 2002
Re: Sonic Impact 5066 Parts List & Modifications
You have left out the input blocking capacitors. It has been suggested that they are limiting the low frequency response. They have to be connected to the 10K resistor setting the input impedance and connected to the input pins of the 2024.
This makes me think there is one on top and one on bottom. I am going to dig in and try and locate them. Bypassing them with a larger valur cap may flatten out the response below 200 Hz.
|8th February 2005, 01:33 AM||#10|
Join Date: Apr 2003
Thanks for your reply. I agree with you that the input caps are most likely the source of low-frequency rolloff on the amp.
C3/4 in the post above are what I believe to be the input blocking capacitors. I'll be replacing those with Solen 5.1uF caps to see if it makes an appreciable difference.
On a side note, I placed my order with Digikey yesterday for the new resistors, caps and other parts. They shipped it this morning, so I should get it in the next few days.
I decided to go with Panasonic 1% resistors for the time being -- It's the same price for 50 of them versus 5 of the 0.1% resistors.
Hopefully this will bring good changes to the amp! To be honest, I really thought this SI stuff was a lot of hype until I put one on my little AR-17's.. I dare say it sounds better than my Panasonic Class-D amp.. It definitely seems to have more "punch" than the Panasonic at 1/20th the power.
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